Unfortunately, the refactoring we have started is not committed yet, so doing modification by yourself is not really possible on the "new code".
However, we are close to finish, so patience is the only option :-)

We are open to contributions but we have no guide yet for this.
People who succeed to understand the code usually send patches by mail, or clone the github tree.

Another way of contribution is to suggest syntax/new feature like you've done.
Skeaking about this and to keep things as simple as possible, we envision to allow brackets after the "end fork" command,
so that you could have: